3-DIMENSIONAL STRUCTURE OF THE RIBOSOMAL TRANSLOCASE - ELONGATION-FACTOR-G FROM THERMUS-THERMOPHILUS

The crystal structure of Thermus thermophilus elongation factor G without guanine nucleotide was determined to 2.85 Angstrom. This GTPase has five domains with overall dimensions of 50 x 60 x 118 Angstrom. The GTP binding domain has a core common to other GTPases with a unique subdomain which probably functions as an intrinsic nucleotide exchange factor. Domains I and II are homologous to elongation factor Tu and their arrangement, both with and without GDP, is more similar to elongation factor Tu in complex with a GTP analogue than with GDP. Domains III and V show structural similarities to ribosomal proteins. Domain IV protrudes from the main body of the protein and has an extraordinary topology with a left-handed crossover connection between two parallel beta-strands.